Generally, an alloy is a eutectic body of one member of metal element, and one or more members of other metal elements or a nonmetallic element such as carbon, nitrogen, or silicon. Generally, an alloy is produced for making properties such as mechanical strength, chemical resistance, corrosion resistance, and heat resistance higher than those of pure metal.
Among various alloys, an aluminum alloy has a light weight and excellent strength, and therefore is used for various applications such as structural materials including building materials and containers, transportation equipment including automobiles, ships, and aircrafts, various electric appliances, and electronic parts. A titanium alloy has a light weight and excellent corrosion resistance, and therefore is widely used for precision instruments, ornaments, tools, sporting goods, medical components, and the like. Stainless steel which is an iron-based alloy, or a nickel alloy, has excellent corrosion resistance, and therefore is used for various applications such as structural materials, transportation equipment, tools, machinery, cookware, and the like. A copper alloy has excellent electrical conductivity, thermal conductivity, corrosion resistance, and processability, and beautiful final conditions, and therefore is widely used for ornaments, eating utensils, musical instruments, and parts of electric materials, and the like.
A surface of an alloy is required to be mirror-finished according to an application. As a method of mirror-finishing, the surface of an alloy is painted or coated. However, if mirror-finishing can be realized by polishing the surface of an alloy, more advantages than painting or coating can be obtained. For example, polishing can provide a better mirror surface than painting, and therefore does not require a painting step or a coating step, and materials used therefor. Furthermore, a mirror surface obtained by polishing has higher durability than a mirror surface obtained by painting, and therefore is maintained for a long time.
Conventionally, mirror-finishing of a surface or smoothing thereof by polishing has been tried (for example, refer to Patent Literatures 1 and 2). However, it is not possible to obtain a higher-quality mirror surface by these methods. Particularly, when an alloy in which a main component and an element having a different hardness from the main component are mixed is polished, various defects such as projections, recesses, or flaws (so-called scratches) are generated on the surface of alloy after polishing. Therefore, it is difficult to obtain a highly mirror-finished alloy by polishing.